rich1.0npub1pmw4p7tz6s8k62zrpdpxc93ajlmpxe0s03j275dcmcejv8wazz9qhe5c0rhttps://nostr.ae/npub1pmw4p7tz6s8k62zrpdpxc93ajlmpxe0s03j275dcmcejv8wazz9qhe5c0rnjumphttps://nostr.ae📅 Original date posted:2018-01-22 📝 Original message:> Most transactions don't have change?! Under what circumstance? For most > use-cases the reverse is true: almost all all transactions have change, because > it's rare for the inputs to exactly math the requested payment. It's actually a common misconception. With good coin selection, I am able to avoid change about ~75% of the time in my simulations (on my real world data). In practice it's a bit lower, probably about 40-50% of the time because of the need to keep the majority of my funds offline where they can't be used for coin selection, and I have not been able to accurate simulate how I consolidate. Also the other misconception is that inputs don't need to match exactly the requested payment, it's totally fine to do something I call a "miner sacrifice" where you overpay txfees up to the amount that that would otherwise be the total cost (immediate + consolidation) of creating change. Also another trick I use, is something I call "output selection". If I have N queued non-time sensitive payments, I don't really need to send them all at the same time. So I can pick the best combination of inputs+outputs. Obviously none of this applies to consumer wallets, who typically have less than a handful of options. But for a service, avoiding change can be the norm with good coin selection. --- -Ryan -------- Original Message -------- On January 22, 2018 3:00 PM, Peter Todd <pete at petertodd.org> wrote: > On Mon, Jan 22, 2018 at 12:40:31PM -0500, Rhavar via bitcoin-dev wrote: > >> So my half-baked idea is very simple: >> Allow users to merge multiple unconfirmed transactions, stripping extraneous inputs and change as they go. >> This is currently not possible because of the bip125 rule: >> "The replacement transaction pays an absolute fee of at least the sum paid by the original transactions." >> Because the size of the merged transaction is smaller than the original transactions, unless there is a considerable feerate bump, this rule isn't possible to observe. >> I my question is: is it possible or reasonable to relax this rule? If this rule was removed in its entirety, does it introduce any DoS vectors? Or can it be changed to allow my use-case? > > It would definitely introduce DoS vectors by making it much cheaper to use > relay bandwidth. You'd also be able to push others' txs out of the mempool. > >> --------------------------------------------------------------- >> >> Full backstory: I have been trying to use bip125 (Opt-in Full Replace-by-Fee) to do "transaction merging" on the fly. Let's say that I owe John 1 bitcoin, and have promised to pay him immediately: Instead of creating a whole new transaction if I have an in-flight (unconfirmed) transaction, I can follow the rules of bip125 to create a replacement that accomplishes this goal. >> From a "coin selection" point of view, this was significantly easier than >> I had anticipated. I was able to encode the rules in my linear model and >> feed in all my unspent and in-flight transactions and it can solve it without difficulty. >> However, the real problem is tracking the mess. Consider this sequence of events: >> >> - I have unconfirmed transaction A >> - I replace it with B, which pays John 1 BTC >> - Transaction A gets confirmed >> >> So now I still owe John 1 BTC, however it's not immediately clear if >> it's safe to send to him without waiting $n transactions. However even >> for a small $n, this breaks my promise to pay him immediately. >> One possible solution is to only consider a transaction "replaceable" if it has change, so if the original transaction confirms -- payments can immediately be made that source the change, and provide safety in a reorg. >> However, this will only work <50% of the time for me (most transactions >> don't have change) and opens a pandora's box of complexity. > > Most transactions don't have change?! Under what circumstance? For most > use-cases the reverse is true: almost all all transactions have change, because > it's rare for the inputs to exactly math the requested payment. > > https://petertodd.org 'peter'[:-1]@petertodd.org -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linuxfoundation.org/pipermail/bitcoin-dev/attachments/20180122/1abc39e2/attachment.html>